//
// Created by madison on 2022/7/11.
//

#include "string"

using namespace std;

/**
 * Definition for singly-linked list.
 **/
struct ListNode {
    int val;
    ListNode *next;

    ListNode() : val(0), next(nullptr) {}

    ListNode(int x) : val(x), next(nullptr) {}

    ListNode(int x, ListNode *next) : val(x), next(next) {}
};

class Solution {
public:
    // 方法一：迭代
    ListNode *reverseList(ListNode *head) {
        ListNode *prev = nullptr;
        ListNode *curr = head;
        while (curr) {
            ListNode *next = curr->next;
            curr->next = prev;
            prev = curr;
            curr = next;
        }
        return prev;
    }

    // 方法二：递归
    ListNode *reverseList1(ListNode *head) {
        if (!head || !head->next) {
            return head;
        }
        ListNode *newHead = reverseList1(head->next);
        head->next->next = head;
        head->next = nullptr;
        return newHead;
    }
};

int main() {
    ListNode *node4 = new ListNode(5);
    ListNode *node3 = new ListNode(4, node4);
    ListNode *node2 = new ListNode(3, node3);
    ListNode *node1 = new ListNode(2, node2);
    ListNode *head = new ListNode(1, node1);
    ListNode *temp = head;
    while (temp) {
        printf("%d\t", temp->val);
        temp = temp->next;
    }

    printf("\n");
    Solution solution;
    head = solution.reverseList(head);
    ListNode *temp1 = head;
    while (temp1) {
        printf("%d\t", temp1->val);
        temp1 = temp1->next;
    }
    return 0;
}